Topaz (8), corundum (9), and diamond (10).
You can determine the streak of a mineral whose Mohs scale is higher than the streak plate by either filing or crushing with a hammer before rubbing the sample on a streak plate.
7 (level of hardness)
Mohs hardness scale
The Mohs Scale of Hardness determines the hardness of minerals by scratching them with commonly found objects. The minerals are assigned a number which corresponds to their hardness; higher numbers indicate higher hardness.
It is the Mohs scale of mineral hardness. It characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. The scale assigns numbers 1-10. 10 being the hardest of minerals(e.g. diamonds), and 1 being the softest minerals(e.g. talc). Generally minerals with a H<5 are softer minerals and minerals H>5 are harder.
A streak plate has hardness of 7 on the Mohs scale, so harder minerals will not leave a streak. Diamond has a hardness of 10 and corundum is 9 - so neither will leave a streak.
Minerals with a hardness greater than around 7 on the Mohs hardness scale will not leave a streak on a standard unglazed porcelain streak plate. They will instead scratch and powder the streak plate.
Diamond will not leave a streak on a porcelain streak plate because diamond is harder than the streak plate. It will leave a scratch on the streak plate for the same reason.
It leaves a scratch instead of a streak because Topaz has a higher number on the Moh's scale compared to the streak plate.
A streak test is used to determine a minerals streak color. This can help in with the identification of minerals. A streak test is performed by rubbing the mineral on an unglazed ceraminc tile, then observing the color of the streak which is left behind. All minerals do not leave streaks. Harder minerals will not streak, but this can also be used as a tool for identifying the mineral, if you are familiar with the hardness scale.
You can determine the streak of a mineral whose Mohs scale is higher than the streak plate by either filing or crushing with a hammer before rubbing the sample on a streak plate.
No it does not work with all minerals. For if you did not know streak plates have a hardness of 7 (maybe a little lower or higher) on the Mohs scale. Some minerals are harder than 7 though. If they are harder they will not work with the streak test. some examples are Diamond, topaz, and corundum.
The hardness of a porcelain streak plate will vary between 6.5-7.5 on the Mohs hardness scale.
7 (level of hardness)
When identifying minerals, having no streak is a property of hardness. A streak plate has a hardness of ~7(Moh's Scale). Thus any mineral having a hardness greater than 7 will have no streak.Metallic is the description of luster. Or the general appearance of a mineral surface in reflected light.If you were refering to the mineral having metal elements in it, streak is actually very useful for identifying them. Many minerals that are composed of non-metals have a white streak which can appear to be no streak, however there are also many minerals with no streak which are composed of non-metallic minerals (Diamond).
The color left on a streak plate when the mineral is scratched on the surface of the plate. Different minerals have different streak colors. The mineral is tested for hardness to see where it lies on the Mohs scale. The crystal structure (othorhombic, tetragonal, triclinic, isometric, monoclinic, or trigonal), will help identify the mineral. Different minerals have different densities and weights.
The color left on a streak plate when the mineral is scratched on the surface of the plate. Different minerals have different streak colors. The mineral is tested for hardness to see where it lies on the Mohs scale. The crystal structure (othorhombic, tetragonal, triclinic, isometric, monoclinic, or trigonal), will help identify the mineral. Different minerals have different densities and weights.